Electronic mail (e-mail) is a method of exchanging digital messages. E-mail systems are based on a store-and-forward model in which e-mail server computer systems accept, forward, deliver and store messages on behalf of users, who only need to connect to the e-mail infrastructure, typically an e-mail server, with a network-enabled device for the duration of message submission or retrieval. It may be sometimes desirable to find similar e-mails located in a database or a collection of e-mails. E-mail thread refer to establishing a relationship within multiple e-mails within a set of e-mails, which may be related.